The conservation question

The Growing Edge

The conservation question

The horticulture industry continues to look at how growers can conserve water in their operations and which crops will require little water in consumer landscapes.

Patrick Williams

At open houses throughout the year, Jared Sisneroz says UC Davis invites members of the horticulture industry and UCCE Master Gardeners to the UC Plant Irrigation Trials to evaluate the plants based on overall appearance, floral abundance and foliage quality.

Photo courtesy of Karrie Reid

As droughts and water scarcity continue to plague North America, operations are aiming to cut costs and consumers are looking for low-maintenance plants. As they become increasingly environmentally minded, members of the horticulture industry are looking at ways to conserve water from propagation to consumers’ landscapes.

Among those industry members are 16 researchers who are part of the Clean WateR3 group, says Alexa Lamm, associate professor and extension evaluation specialist at the University of Georgia. Founded in 2014, Clean WateR3 is federally funded through a Specialty Crops Research Initiative grant and focuses on helping growers reduce, remediate and recycle water.

“We’re at the end of our project now,” Lamm says. “We’ve been working on this stuff for a long time, but this is when you’re going to see all of the articles that have gotten through the peer-review process and everything start to really come out.”

Meanwhile, on the West Coast, University of California Plant Irrigation Trials Project Manager Jared Sisneroz trials plant varieties and some natives with low-water use requirements near the UC Davis campus. He says the trials don’t just have value in the West where water availability is top of mind.

“Low-water-use plants are really valuable [in the landscape]. Because if you think about in areas where there is maybe not scarcity, but pressures on water supply — if you can reduce watering from three days a week to every two weeks or once a month, or even three times over the summer, that kind of reduces a lot of costs upstream,” he says.

How growers can conserve water

Tom Fernandez, a professor in the Department of Horticulture at Michigan State University, says conservation starts with understanding how much water a plant needs. The Clean WateR3 member focuses on water quality and management, including ways to conserve water through various irrigation methods.

He says growers should not irrigate with a fixed amount, but rather by “replacing the amount of water that the plant uses on a daily basis.” Growers can use sensors to measure how much water leaches out of a container or consult a publication from their state’s extension to irrigate based on this “leaching fraction.”

Certain irrigation systems, such as flood floors and ebb-and-flow benches, also conserve water because they recapture and reuse it, Fernandez says.

“Every time you reuse an original pumping of water, you increase your efficiency, and you’re basically increasing your conservation of that resource, so you’re utilizing it multiple times,” he says.

Measuring adoption

For a Clean WateR3 study, Lamm and other researchers in the group measured the adoption of water-conservation techniques. They found that adoption largely rested on growers’ ability to observe new water-conservation technology — perhaps in a video online, at a field trial or at another nursery or greenhouse — and trialing it.

“So one of our recommendations that came from that was creating kind of a mentoring program, maybe with our commodity groups within the industry, where growers can go to each other’s facilities when they know someone’s adopted something, and partner them with another grower where they can go and try and see what they’re doing at their facilities so that we can increase the rate of adoption,” Lamm says.

The researchers also found that “relative advantage” — the discovery that using one technology could be advantageous over another — influenced greenhouse and nursery growers in their decisions of whether to adopt it.

Some growers use flood floors (pictured) and ebb-and-flow benches to recapture and reuse water.

Photo courtesy of Sarah White

Economic advantages and disadvantages

Growers have many factors to consider when determining the relative advantage of a new water-conservation technology. One of the big ones — costs — can be complicated, Fernandez says.

In the West, many growers pay for water by the acre-foot, so the savings is often clear, he says. But in the East, many growers don’t pay for water paying instead just to pump it. As a result, some growers end up using more than they need.

No matter the region, though, Fernandez notes that costly problems often occur when water pools or is otherwise in abundance in a greenhouse or nursery. So taking steps to reduce those water levels can reduce or eliminate hidden costs.

“A lot of pathogens like a lot of water around or need water around to spread or become infectious,” he says. “Weeds, of course, will thrive with more water. Insect pests usually feed more on lush, rapid growth that excess water creates. The more you irrigate, the more you’re washing off your pesticides, herbicides, and then you’re also flushing nutrients out.”

In 2010 and 2011, McCorkle Nurseries in Dearing, Georgia, used sensors to monitor and reduce its irrigation of gardenias. It also cut its production cycle down from 22 months to 11 months, making a more than 150-percent gain in annualized profit, according to the study “Profitability of Sensor-based Irrigation in Greenhouse and Nursery Crops." Fernandez points to the study as an example of a success story that shows how water conservation can reduce costs.

But Lamm shares a different kind of story regarding water conservation and costs. She says she met with a grower in Florida who didn’t have much to gain financially from installing a rainwater recapture system, but he still went through with the project.

“It cost him an exorbitant amount of money that he will never recover; it’s not cost-effective for him,” she says. “But he wanted his consumers to see him as environmentally conscious — environmentally friendly.”

Lamm also notes that drip irrigation better conserves water and ensures its availability than an overhead sprinkler system. Some growers may switch out the entire system, even if they will never recover the cost of doing so.

“Even though they know there’s a relative advantage in terms of environmental concerns and ensuring water availability, financially there’s not an advantage — there’s a big disadvantage,” she says. “And so it’s kind of weighing one against the other.”

Environmental concerns and water regulation

Many decisions regarding water conservation are ultimately responses to environmental concerns — concerns of growers, of consumers, of the government or perhaps some combination.

During the height of the drought in California, then-Gov. Jerry Brown banned irrigation of landscapes for two days after measurable rainfall. Then, more than a year after he declared the end of the drought, Brown set permanent restrictions on residential indoor water use and announced there would be residential outdoor water restrictions based on regional climates.

In addition, an executive order Brown signed in 2015, which is still in effect, created requirements for irrigation to landscapes, the number of “high water use plants” that could be used, and more, according to the California Department of Water Resources.

“So there’s a tremendous need for finding a quality low-water use plant material, especially because you are now required to have water budgets for basically all new landscapes,” Sisneroz says.

But it’s not just California that can benefit from low-water use crops, Sisneroz says.

“For instance, while California is in a drought, Arizona and New Mexico aren’t exactly rolling in water, nor [are] Nevada, Utah or Colorado,” he says, adding that UC Davis is considering expanding low-water use trials to other Western states such as Arizona, Colorado, Oregon and Washington to put less pressure on the region’s aquifers.

Even for those growers in the East who don’t need to reduce their water use for now, Fernandez says many of them are seeing the benefits of cutting back.

“I think [it’s] becoming more and more common that growers are either seeing [water conservation] as a benefit because there are environmental costs to overirrigating and then your runoff leaving your site,” Fernandez says. “So building retention basins to capture and then recycle the water is becoming more common. Other operations are understanding that regulations might be coming, and so if they’re installing new production facilities or retrofitting old ones, they’re doing that with water recapture in mind, so that if they ever need to, they have the capacity.”